High Rapid RH readings??

[ddemento]

Hi, I'm new to using rapid RH and concrete moisture testing and would appreciate any feedback on the following:
Conditions:
-New 2500sq.ft. slab 6" thick installed over vapor barrier over 12" gravel foundation.
-trowel finished with no other products added (no sealer or other)
-installed 3 RH probes at 40% depth after 1 month of pour. Sensors read 97% after 1 hour and 99% ever since.
-Its now been almost 3 months since the end of the water cure and still 99%RH from all 3 probes
-The RH in the gym was about 50% and is now 30% for about a month already. Temp. of gym has been around 70 F
Questions:
-Is it normal to still have 99% while other test types have shown a drop?
-Are the probes malfunctioning and should I have waited longer prior to installing them?
-Should I go ahead and install another probe to be sure of the readings?

Thanks.