A couple river folds

These seem to be good folds, but they've been happening a lot lately. So I need a checkup.

The turn is also questionable... I will bet these quite often (especially hand 2), but in these hands I chose to check.

First hand:

1/2 6-max, no reads on villain but he has a big stack.

I have J4 in the BB and check my option.
Flop comes 356 two clubs (I have none).
I lead for $6 into the two limpers.
Villain calls in the SB.

Turn is the 7 of clubs. check/check.

River an offsuit A.
Villain checks and I bet the pot, villain raises me 3x my bet.


Second hand:

2/4 full ring, again no reads but I'm up a buyin at the table, playing tightish.

I limp QJs in the hijack with a few others.

Flop comes 39T one spade.
Checked to me and I bet the pot, MP calls.

Turn a low spade, check/check.

River is an offsuit Q.
MP checks, I bet 3/4 pot, he raises me 3x my bet.