The top picture is interveinal chlorosis and that could be related to high pH inducing either iron and/or manganese deficiency. I'm assuming this is on the youngest centre leaves primarily? The other two pictures aren't chlorosis. I've seen something like the middle one, it may be insect damage but unless you see it on a lot of leaves I wouldn't worry about it. The last one looks like variegation - is it the only leaf in the clump that is doing this?
Edited - forgot to add that you can temporarily lower the soil pH around the affected plant with one teaspoon of vinegar in one litre of water poured around the plant once a week and see if that fixes the problem. If it does then you may need to look for a more long term solution but try this treatment - only on one or two plants to start with in case there's no benefit or worse! Don't make the solution any stronger than that.
