Let me point out a few faults here.. First you bought good batteries so go buy a REAL hygrometer. temperature compensated floating glass, not a floating ball. A tiny air bubble could cause a ball to float that shouldn't and they are to inaccurate to start with.
Next new batteries are stored and shipped with some sort of protective coating on the terminals , this prevents discharging while stored, or slows it down. the felt washers are to prevent corrosion if there is a bad seal/leak around the terminal.They can neutralize any acid that leaks there.
Electrical connections should be clean and dry, and kept that way. DO NOT use grease,vaseline or any other non drying coating on terminals.It can run in between terminals when it gets warm.insulating them.
I use a drying rubberized coating to keep corrosion down. paint works ok but the rubberized coating peels off easily.
To test a connection, use a multimeter on each side of your terminals,(one on batt. term. 1 on cable clamp) there should be no resistance.
For more procedures refer to my battery FAQ in the FAQ's section.