Castleford failed to arrest their slide as their batsmen were blown away by Yorkshire Premier League North leaders Harrogate.
Set 201 for victory after a decent effort in the field when they had pulled off four run-outs to back up the bowlers well, all the good work in the first half of the match was undone by a poor effort with the bat.
Skipper David Wainwright, after a number of half centuries in recent weeks, moved himself up to the top of the order in an effort to give Cas a good start, but the move did not work as he lasted just 11 balls, scoring one run.
Fellow opener George Swaby was out for five after surviving just nine balls and number three Mohammad Waqas was adjudged lbw without score, leaving the reply soon in deep trouble at 8-3.
James Sykes tried to hold the rest of the innings together with a battling knock of 23, but with no-one else able to join him in reaching double figures there was no recovery with Castleford all out for 64 in the 34th over.
David Foster did much of the damage with 4-35 while Nick Taylor claimed 3-17.
Harrogate had earlier failed to make the most of a good 78-run opening stand between Matthew Good (26) and Dion Sanson (31) as Castleford bowlers kept chipping away with wickets and the four run-outs kept the hosts in check.
Wainwright was the pick of the Cas bowlers with 3-25 from 16 tidy overs while Eddie Morrison took 2-63 as Harrogate were all out for 200 in the 47th over.
Castleford seconds were also beaten in the York League’s Ebor Division Three despite a superb century from Eddy Cole.
Cas produced one of their best batting displays of the season as they piled up 231-5 with Cole leading the way with an unbeaten 124 and support coming from Tomlinson (34) and Nathan Smith (39).
But they were up against championship-chasing Whitkirk II, whose batsmen also found conditions to their liking as they reached their target with surprising ease, only losing four wickets.
Castleford under 19s had mixed fortunes in two Yorkshire North T20 matches.
They lost by two runs to Hull under 19s after making 142-5 in reply to 144-8, but bounced back to beat Beverley under 19s by six runs after posting a 139-3 score.
Castleford under 11s went down by 20 runs to Fairburn in the Pontefract Junior League as they were kept to 36-3 in reply to 56-3, Isack Newrick (9) top scoring and Jaden Hughes, Newrick and Pierce Memerry taking a wicket each.