spots where i cbet and gave up (3 random hands)

Rong just sweated me and it seems that I fire again on turns far less frequently than he does, so it got me looking into the database for some hands to investigate.

Hand 1. Villain is 50/3.

PokerStars No-Limit Hold'em, $0.05 BB (5 handed) - PokerStars Converter Tool from http://www.flopturnriver.com

SB ($5.02)
BB ($5)
UTG ($9.69)
MP ($10.60)
Hero (Button) ($7.55)

Preflop: Hero is Button with A, K
UTG calls $0.05, 1 fold, Hero bets $0.25, 2 folds, UTG calls $0.20

Flop: ($0.57) 3, J, Q (2 players)
UTG checks, Hero bets $0.30, UTG calls $0.30

Turn: ($1.17) 9 (2 players)
UTG checks, Hero checks

River: ($1.17) 5 (2 players)
UTG checks, Hero checks

Total pot: $1.17 | Rake: $0.05

Results below:

Spoiler: Show

Hero didn't show A, K (nothing).
UTG had A, 8 (flush, Ace high).
Outcome: UTG won $1.12

Hand 2. Villain is 42/14

PokerStars No-Limit Hold'em, $0.05 BB (5 handed) - PokerStars Converter Tool from http://www.flopturnriver.com

BB ($10.89)
UTG ($14.68)
MP ($11.66)
Hero (Button) ($5.11)
SB ($1.23)

Preflop: Hero is Button with A, 10
2 folds, Hero bets $0.10, SB calls $0.08, 1 fold

Flop: ($0.25) 7, J, 5 (2 players)
SB checks, Hero bets $0.20, SB calls $0.20

Turn: ($0.65) 2 (2 players)
SB checks, Hero checks

River: ($0.65) 9 (2 players)
SB bets $0.93 (All-In), Hero folds

Total pot: $0.65 | Rake: $0.03

Results below:

Spoiler: Show

SB didn't show

Hand 3. Villain is 38/32/23 and is aggressive postflop.

PokerStars No-Limit Hold'em, €0.05 BB (5 handed) - PokerStars Converter Tool from http://www.flopturnriver.com

SB (€4.89)
BB (€5.90)
UTG (€3.69)
MP (€7.36)
Hero (Button) (€5.05)

Preflop: Hero is Button with 7, A
2 folds, Hero bets €0.15, 1 fold, BB calls €0.10

Flop: (€0.32) 2, 3, 9 (2 players)
BB checks, Hero bets €0.15, BB calls €0.15

Turn: (€0.62) 9 (2 players)
BB checks, Hero checks

River: (€0.62) K (2 players)
BB checks, Hero checks

Total pot: €0.62 | Rake: €0.03

Results below:

Spoiler: Show

Hero had 7, A (one pair, nines).
BB had 5, A (one pair, nines).
Outcome: Hero won €0.59

Common theme, my bet sizing on flops are probably mostly too small, and on turns for that matter also, but we're looking at spots specifically where I chose to check instead of betting again. Exception hand 2 where the flop sizing seems larger than normal, but I think I was planning on barrelling on turns that give us extra equity? Is this poor thinking?