Fruit Beer Finishing Too Thin

Hey fellow brewers really having an issue with my fruit beers finishing too thin lately. I used to do extract and my first fruit beer I steeped 1lb. carapils and put the fruit in the primary.

Now I do a partial mash or BIAB style and did .75lb carapils, same amount of fruit (5lbs frozen blackberries) and I put the fruit in the secondary. Except my last few batches have turned out really thin and tart and I'd really like to get them back to the way they tasted before without steeping my carapils.

Suggestions?

Mash higher?

According to my notes I mashed at 154F. Not that it matters really, but I steeped my grains during the extract brew at 155F. I may take a look at my thermometer and make sure its still calibrated properly and really make sure I hold the 154 to 155 mash temp?
It just seems odd to me that the beer is so thin now considering that I'm putting the fruit in secondary rather than primary and only backed my carapils down by 1/4lb. I even upped the amount of crystal 10 and honey malt I used too

What yeast are you using?

Well I've actually used 3 different yeast strains now. First I used a british ale yeast from white labs, then I switched to a cream ale blend since it is a cream ale. Then I moved and I think the LHBS only carries Wyeast so I used their Kolsch yeast for the latest batch. I did have success using both the british ale and cream ale blends back when I did the batch with extract and grains. It seems that my problems started when I moved over to partial mashes. It's as if the carapils is being converted, but shouldn't it still contribute dextrins regardless of whether it's steeped or mashed?

When you used extract you added 1 pound of carapils to an extract that likely had carapils in it so you had doubled the carapils amount. Now when you did the all grain you decreased the carapils to .75 pounds and had none in extract so you have really decreased the carapils. If you can find the brand of extract you may be able to search out what amount of carapils it had in it.

Well the thing is I am still using extract, but I am doing a little partial mash. So I'm putting the carapils, a pound of pale malt, and my crystal malts in roughly a gallon of water and letting them sit for about 45 minutes at 154F. During my extract with grains, I had 1lb. carapils, 1lb. flaked maize, and I believe 1lb. pale malt, but I had steeped it in 3 gallons of water for 30 minutes. So I figure I got a lot of unfermentables from that steep in part because of the time, but also because of the large water volume. Now I'm doing it for longer and adding crystal 10 and honey malt and still getting an incredibly thin beer in comparison to before. Is it possible I got that much more unfermentables and starches from the steep? How much carapils would I add to my mini-mash to compensate? Would maltodextrin be better, or perhaps use a puree instead of real fruit?