Yellow spots on cycas

[Nickz]

I have 2 cycas plants in two identical pots, similar size, same potting mix. Both show yellow spots on their leaves:

Spots appear to be just discoloration of the leaves, can't be removed or felt by touch. There are almost no spots under the leaves. The most fitting cause i found online is some kind of pest that could have left these marks after bitting the plant. I didn't pay much attention but at the moment i can not see any kind of pest. Is there another explanation? What should i do now other then paying more attention in the future?
Thanks

 

[Tetters]

This could possibly be a manganese deficiency. You could have a look at spraying with manganese sulphate. These plants need soil that is not too alkaline, nor too acidic. I hope you can save it, and I wish you luck.

 

[Nickz]

This could possibly be a manganese deficiency. You could have a look at spraying with manganese sulphate. These plants need soil that is not too alkaline, nor too acidic. I hope you can save it, and I wish you luck.

Thanks. I can check the ph of the potting mix, should be 6.5 if i remember correctly. I already gave some slow releasing fertilizer that contains manganese as well two weeks ago, that might be enough. I will monitor the plant to make sure it does not get worse.