I noticed this thread is a few months old, but I figure I'd throw in my $0.02.
I can confirm that it is not very efficient to redose mushrooms once the initial effects take hold. When I eat more mushrooms a few hours into the experience, I do notice this adding to the trip after a while, but the effect is far weaker (like 2.5 grams feels more like a small gram or so for me). It can stretch the trip out a bit, but doesn't intensify it that much and often feels a bit wasteful imo.

From your description it sounds like a combination of the redosing problem I described above, and a weaker batch of mushrooms. Also keep in mind that eating them on an empty stomach often makes quite a difference.
I had a similar issue on my last mushroom trip. I have grown these mushrooms myself, and they were definitely quite potent in the beginning. However, when I last ate them they were already over a year old and there was an obvious loss in potency (mushrooms were double-bagged in ziploc bags and stored in a cool, dark cupboard). I weighed off 3.1 dried grams and only reached slightly above-threshold effects. Fairly full-on body high, increased visual acuity, peaceful state of mind and some fluid, emotional thoughts, but no visuals whatsoever besides the HD-vision. I was definitely beyond the dreaded "inbetween state" (which OP seems to have experienced), but not quite there yet. I find some potent sativa weed synergises nicely with a low-dose mushroom trip, however I don't (or hardly ever) smoke on full-on trips.

I should definitely take the opportunity to give the lemon tek a try with my weakened old mushrooms. And afterwards start a new grow, obviously