Westinghouse FT4be-030k 410a. I had a tune-up late Nov., Tech found a leak where you hook up the gauges to check pressures and he replaced the valve. He suggested a leak test but I elected to hold off to see if this was the only leak. The outside temp was 53 and he added Freon to 90 low and 320 high. Looking at the charging chart for heat mode at 50 degrees, it calls for 110 low and 382 high. Am I still low on freon everything else being ok? I am down about 3 or 4 degrees at supply vs. last winter and may have a defrost problem. Should I have him back to add more and then do the sub cool thing this spring?