Based on @Buckly 's suggestion for making the different membrane types more destinct i would like to mention a key changes that would make for more scientific accuracy and potentially provide a few interesting ramifications in the later stages.
i think that calcium carbonate should continue to have a significant chemical resistance at the cost of lower chemical damage and silica to have lower chemical resistance in exchange for higher chemical damage as a silica cell wall contains many small gaps so as to exchange material and so toxins can still diffuse into the cell but are less likely to diffuse out of the cell. Calcium carbonate on the other hand is chemically active and likely to react with most agents reducing their damage to the cell membrane beneath.
Silica cells can also build up more pressure when firing toxins and calcium carbonate cells will have a portion of their chemichal damage lost to the toxins reacting with the cells own wall.
This will also have the effect that in the later stages silica organisms will have a mutch higher investment in chemical warfare.
Any other ideas on improving the membrane types
(This is my first post)