My Java Ferns are starting to get clear tips. About 1/4 of the end of
the leaf is starting to turn clear on the newer leaves.

Also sections of the leaves are turning black, but are still growning.

I have several other plants in the tank growing well. Could the other
plants be stealing minerals away from the ferns? Root ans such look
healthy.

I have a DIY CO2 and fertalize with the standard pet store fertalizer.
(though CO2 has been having problems) 3- 40 W Bulbs on 70 gallons. No
special substrate. Do not do water changes as much as I should.

I dont think I have too much light. I think I have a mineral shortage.
What do I do to add more minerals? What mineral do I need.

Not looking to spend an excessive amount. I was thinking about getting
pond tabs and breaking them up.

Thanks,
Martin