I read to use bicarb to remove powdery mildew on plants. I did this with a t
(tiny) bit of water and then wiped dry afterwards, on my flaming Katy plant. The plant was robust and healthy and immediately after doing this, the whole stem and leaves are limp, that it is bent fully over. I know it absorbs water through its leaves as a succulent but I hardly used any water, and I wiped it straight away, it wasn't covered in water.
I can't find an answer to this online.
Does bicarb make house plants limp? Is this plant having a bad reaction?

I previous did this on the mother plant that had powdery mildew and it didn't recover, the leaves were super limp for weeks immediately afterwards and looked really unhealthy. I thought maybe it was because I didn't wipe the excess water off the leaves, as the treatment had this immediate affect. I took a cutting and this was with the baby plant I refer to above! Except I WAS happy because it was looking really healthy and strong (just started showing the mildew). The same thing has happened again immediately after treatment (except this time I wiped it and there wasn't much water).
Edit: the few minutes after post the leaves look burnt, floppy and are falling off on where I put the bicarb! Why is it recommended to use this but ruined my new cutting! I did add a tiny bit of washing up liquid to the mix, I'm not sure why I did that, I don't know if that is the cause of this?

Something is wrong. A teaspoon of baking soda (bicarb) well dissolved in water should not kill your plants and you shouldn't need to wipe it off.

I'm having trouble interpreting how much water you used. You wrote "I read to use bicarb to remove powdery mildew on plants. I did this with a t
(tiny) bit of water and then wiped dry afterwards. ... I hardly used any water, and I wiped it straight away..." Do you mean you made a gritty paste? And then rubbed/wiped it? That's what has damaged the leaves; you essentially sanded them. You want to spray highly diluted bicarb and let it dry with good air circulation, not in direct sun. As with all homegrown recipes, ratios vary by source. I've seen 1 tsp per liter and 1 tsp per gallon. Many recipes add dishwashing detergent, I don't agree with that. If you feel the need to add a sticking agent, use true soap like castille. For indoor plants, I'd go with the greater dilution.

Please clarify if I've misunderstood how you applied the bicarb. Meanwhile, here's a site that describes the process.

https://www.thespruce.com/baki....

There is an outer layer on all plants (the cuticle) that protects the plant from moisture loss (among other things). If the cuticle is damaged or destroyed for some reason (for instance, someone sprayed them with bicarb and detergent. Oops!), the plant will react almost immediately.

If you have a continuing mildew problem, you have an environmental issue you need to solve. Succulents are very prone to mildew if there isn't good airflow.

If the soil is dry, it might be limp from thirst.

Ohhh I see. Yes I made a paste not a spray

It only went and leaves damaged after the application so it's definitely not dry soil or overwatering. Using a paste and cotton swab on leaves definitely now makes sense to of caused this rather than a spray (I didn't want to leave water on this succulent!)
Unfortunately plant hasn't recovered and still limp. Poor thing.
Thank you

Okay. Well, lesson learned: don't use buffing compound on leaves!

Give it some time, maybe cut the stalks back by half. It might send out new growth.

Sodium is essential to normal plant growth, but is also toxic at extremely low levels. When using baking soda around plants it's important to cover the soil when it's applied and the first time water is sprayed on foliage. The poison is in the dosage.

Al